Preset pendulum apparatus

ABSTRACT

An integral cast escapement body with pallets, and preferably also a pendulum holder with a guide groove for inserting a pendulum, are secured to a shaft, preferably by injection molding. The escapement body has two abutment faces at right angles equally spaced a predetermined angle from an axial plane of symmetry in which a balance wheel is located which engages cam faces of integral pallets of the escapement body. By securing the pendulum holder to the shaft spaced the predetermined angle from stationary setting surfaces on which the abutment faces abut, it is assured that the pendulum holder and pendulum are in the center position of angular oscillation when the balance wheel engages the cam faces of the pallets.

United States Patent [191 Wittner PRESET PENDULUM APPARATUS Inventor: Rudolf Wittner, Johnstrasse 6, 7972 'lsny, Germany Filed: Dec. 19, 1972 Appl. No.: 316,555

[30] Foreign Application Priority Data References Cited UNITED STATES PATENTS 5/1972 Wittner 58/130 R [11] 3,817,027 June 18, 1974 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Vit W. Miska Attorney, Agent, or Firm-Michael S. Striker [5 7] ABSTRACT An integral cast escapement body with pallets, and preferably also a pendulum holder with a guide groove for inserting a pendulum, are secured to a shaft, preferably by injection molding. The escapement body has two abutment faces at right angles equally spaced a predetermined angle from an axial plane of symmetry in which a balance wheel is located which engages cam faces of integral pallets of the escapement body. By securing the pendulum holder to the shaft spaced the predetermined angle from stationary setting surfaces on which the abutment faces abut, it is assured that the pendulum holder and pendulum are in the 7 center position of angular oscillation when the balance wheel engages the cam faces of the pallets.

8 Claims, 7 Drawing Figures mamzmumm 3817027 SHEU 2 0F 3 I Fig. 2

PATENTEUJUII 1 a mu SHEET 3 BF 3 Fig; 7

1 PRESET PENDULUM APPARATUS BACKGROUND OF THE INVENTION The present invention relates to a pendulum apparatus for marking exact time, particularly in music or for medical purposes, and generally known as a metronome.

Apparatus of this type has a pendulum fixedly secured by a pendulum holder to a control shaft, and maintained in an oscillating condition by a balance wheel whose teeth successively engage pallets of an escapement means secured to the shaft.

The pendulum of a metronome or similar pendulum apparatus, is subjected to small impact forces by the teeth of the balance wheel, so that the energy loss due to bearing friction'is compensated, and the pendulum swings at an uniform and equal amplitude. In order to prevent the impact of the teeth of the balance wheel from influencing the oscillation time of the pendulum, the teeth must engage the slanted cam faces of the pallets at the moment in which the pendulum passes through the center position of its oscillation. Since the motion of the balance wheel, which produces the drive impacts, is controlled by the escapement and its pallets, greatest precision regarding the mutual setting of the escapement and pendulum, or pendulum holder, on the shaft is of greatest importance during assembly.

The mutual positioning of the parts of the mechanism is very time comsuming and requires great experience, and 9 the escapements according to the prior art are very difficult to assemble.

SUMMARY OF THE lNVENTlON It is one object of the invention to improve the escapement means of a metronome or like pendulum apparatus so that during assembly, the relative position of the pendulum and pendulum holder on the shaft in relation to the pallets can be accurately, and quickly determined with great precision.

Another object of the invention is to preset the relative angular position between the escapement means with the pallets, and the pendulum holder and pendulum, so that the balance wheel engages the pallets at the moment in which the pendulum is in its center positlon.

Another object of the invention is to provide an integral injection molded escapement body which can be inexpensively manufactured and secured to the shaft of the escapement mechanism.

With these objects in view, the escapement body has at least one planar abutment face extending over the entire length of the escapement body, and being located on a side of the escapement body remote from the balance wheel. The abutment face, or abutment faces, permit, during the assembly of the escapement on the escapement shaft, engagement of the abutment face or faces with a setting surface of a setting device which has a predetermined angular distance from the pendulum holder and pendulum before the armature is placed on the escapement shaft and secured thereto. The abutment face engages the setting face of the setting device, so that the correct angular position of the pendulum and pallets is obtained. Such a presetting of the apparatus is not possible with escapements according to the prior art in which the ends of the escapements are only formed by thin escapement pallets.

Due to the small size of the escapements used in metronomes, it is advisable to provide on the escapement body, two substantially perpendicular abutment faces, so that the armature body can be precisely oriented by corresponding setting faces during assembly.

The cost of manufacture of an escapement body according to the invention is a minimum when the escapement body is an integral injection molded body. The escapement body may be cast of a suitable metal alloy, but it has been found particularly advantageous to injection mold the escapement body and the balance wheel of a synthetic material such as polyamide, and to use a harder material for the escapement body than for the balance wheel. The integral, injection molded escapement body of the invention has a substantial cost advantage as compared with known escapement constructions. While the escapements according to the prior art consist of two pallets and a spacing bushing, each of which part requires substantial work, such as drilling and turning of the bushing, stamping, milling and hardening the pallets, and further grinding and polishing the cam faces of the pallets, and finally the riveting together of the three parts, all these operations are eliminated by the integral cast escapement body of the invention.

In a preferred embodiment of the escapement body of the invention, the two abutment faces are the lateral bottom faces of the escapement body which is formed as a rectangular prism and is penetrated by the escapement shaft, pallets being secured to edges of the prism extending across the axis of the escapement shaft, and being curved.

It is advantageous to select the size and shape of the cam faces of the pallets which cooperate with a piece of the balance wheel, in such a manner that they correspond to associated dimensions of the pallets of escapements of conventional construction, so that it is not necessary to make any changes in the construction of the balance wheel or in the mounting of the escapement shaft in bearings. The dimensions of the pallets correspond to the dimension of the pallets used in conventional metronomes. Such an arrangement of the pallets can be obtained with the prismatic escapement body of the invention if on the top basis of the rectangular prism, a semi-circular projection, penetrated by the escapement shaft, is formed whose diameter is less than the length of the basis. The curved pallets radially project from the axial ends of the semi-circular projection.

The curved pallets are connected at the lower ends to lateral marginal face portions on opposite sides of the semi-circular projection, and are consequently very rigid.

Cam faces are provided on the front and rear of the ends of the pallets, the front cam faces being engaged by the teeth of the balance wheel, and the rear cam faces assuring releasing of the pallets by the teeth of the balance wheel. The rear cam faces preferably extend from half the radial height of the pallets to the outer circular surfaces of the pallets.

The handling of the escapement for setting the same relative to the pendulum holder on the escapement shaft, can be, in accordance with the invention, carried out in a particular advantageous manner, if the escapement body is injection molded to the escapement shaft. It is advantageous to provide a circular groove in the section of the escapement shaft which is surrounded by the cast escapement body, so that a reliable connection is assured. In order to prevent any turning of the escapement body relative to the shaft, it is advantageous to provide radial projections in the annular groove, for example to knurl the bottom of the groove.

Finally, the exact mutual setting and attaching of the escapement body. and of the pendulum and pendulum holder can be obtained when the pendulum holder is also injection molded and cast directly on the escapementshaft. Preferably both parts are cast of the same material, preferably a synthetic material such as polyamide.

The section of the escapement shaft which is surrounded by the injection molded pendulum holder, is advantageously also provided with a circumferential annular groove which has radial projections or is knurled. By simultaneously casting the escapement body and the pendulum holder to the escapement shaft,

the cost is reduced to a minimum as compared with other types of metronomes.

The novel festures which are'considered as characteristic for theinvention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a side view, partially in broken off section, illustrating a metronome provided with an embodiment of the invention;

FIG. 2 is a fragmentary side view illustrating a detail of FIG. 1 on an enlarged scale;

FIG. 3 is a sectional view on an enlarged scale taken on line 3-3 in FIG. 2;

FIG. 4 is a fragmentary, partly sectional view taken DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a metronome has a casing I0 which is closed in front by a closure plate 11. A supporting frame 15 is secured to the inner surface of the closure plate I], and supports a spring housing 16 in which a spiral spring is located. The gear teeth 17 on the spring housing 16 mesh with a pinion 18 secured to a balance wheel 20, best seen in FIG. 2, which has spaced slanted teeth 62 cooperating with anescapement means or body 25 which is secured to an escapement shaft 27.

Escapement shaft 27 is mounted on the support frame 15 in a bearing 28, and is mounted at the other end in a bearing bracket 30 on the closure plate 11. Between the bearing bracket 30 and the closure plate 11, a pendulum holder 3l-is fixedly secured to the escapement shaft 27, and supports a pendulum which is mounted on the shaftportion 32 of the escapement shaft 27. The pendulum 33 is mounted in a groove 34 .tween the planar abutment surfaces 36 and 38 being rounded off at 40.

Bymeans of the planar lateral abutment surfaces 37 and 38, the escapement body 25, 36 can be placed between two corresponding setting surfaces 39 of a setting device, not shown, so that the escapement body 25 is exactly positioned in relation to the groove 34 of the pendulum holder 31. In this manner, it is assured that every time the pendulum 33 moves through the center position of the oscillation, one of the pallets 42, 44 receives an accelerating impact on its cam face 63 by a tooth 62 of the balance wheel 20 so that a force component acts on the escapement body 25 to drive the escapement shaft 27 and the pendulum means 31, 33.

The planar abutment surfaces 37, 38, which extend at right angles, are located below the horizontal plane passing through the axis of shaft 27. Horizontal planar marginal faces 58 and are formed'in the horizontal plane, and between the inner edges of the marginal faces 58 and 60, a semi-circular radial projection 48 surrounds the upper portion of the escapement shaft 27. The lower portion of shaft 27 is located in a corresponding opening in the prism 36. The curved pallets 42 and 44 radially-project from the semi-circular projection 48, and are located at opposite axial ends of the escapement body 25, as best seen in FIG. 5. The partcircular outer surfaces of the pallets 42 and 44 form edges 54 with the planar abutment faces 37 and 38, which are extensions of the edges formed between the abutment faces 36 and 38 and the marginal horizontal faces 58 and 60. The pallets 42 and 44 extend along edges 50 and 52 at the axial ends of the marginal faces 58 and 60. Since the pallets 42 and 44 are circular and have centers in the axis of shaft 27, the outer surfaces of the pallets 42 and'44 are spaced the same radius from the axis of shaft 27.

The ratio of the diameter of the semi-circular projection 48 to the distance of the parallel edges 54, 56 is selected so that the curved outer surface of the pallets 42, 44 have a common center in the axis of the shaft in which also the center of the semi-circular projection 48 is located.

The semi-circular projection 48, and the marginal faces 58, 60 which are located in a horizontal plane passing through the axis of shaft 27, achieve a comparatively small radial extension of the pallets 42 and 44 assuring great resistance against the impacts produced by the teeth 62 of the balance wheel 20, which is further improved by the integral construction of pallets 42, 44 with the prism body 36.

As best seen in FIG. 5, the pallets 42 and 44 are spaced such an axial distance that the tooth 62, shown in broken lines, of the balance wheel 20 passes through the space having the axial length d during the osciallation of the escapement body.

The upper ends of the curved pallets 42, 44 project substantially equal distance beyond a vertical plane of symmetry passing through the axis of shaft 27, as shown in FIG. 5. At the free endsof pallets 42, 44, on the side engaged by the teeth'62, cam faces 63 are provided which are slanted 45 to the axis of the escapement shaft 27 and of the escapement body 25. The teeth 62 slide off the cam faces 63 so that a force component perpendicular to the axis of shaft 27 acts to apply accelerating forces to the shaft and pendulum means 31, 33.

The cam faces 63 of the pallets 42 and have a comparatively small width, and merge by rounded off edges into the adjacent surfaces. On the other side, the pallets have a releasing cam face 64, which at the forward end of the pallets has its maximum width, and tapers to the rear. The cam faces 64 which extend substantially from half the height of the pallets to the upper outer pallet surface, assure that the teeth 62, particu larly when they engage the cam faces 63 at an acute angle to the axis of shaft 27, separate from the cam face 64 already after a small turning angle of the balance wheel 20. i

As noted above, the escapement body 25 is a single integral body preferably consisting of a synthetic material, and being injection molded to the escapement shaft 27. ln order to secure escapement body 25 in axial and circumferential directions, an annular groove 68 is provided in shaft 27 which is provided with radial projection such as knurling which are covered by the cast material.

Preferably, the pendulum holder 31 is also directly injection molded onto shaft 27, and for this purpose, an annular groove 70 is provided which is also knurled to prevent turning of the pendulum holder 31 on shaft 27, as well as axial movement.

It is advantageous to simultaneously cast the escapement body 25 and the pendulum holder 31 to the escapement shaft 27, and to make these parts of the same material such as polyamide. ln this event, the pendulum 33 can be mounted on the end portion 32 of escapement shaft 27, and also embedded in the cast material so that an axial displacement of the pendulum 33 in the holder 31 is no longer possible. In this manner, a complete escapement means is obtained in which the simultaneously cast escapement body 25 and the pendulum means 31, 33 are located spaced from each other a predetermined angular distance.

It will be understood that each of the elements described above, or two or more together,.may also find a useful application in other types of pendulum apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in a metronome having an injection molded integral escapement body with pallets and provided with an abutment face, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore,'such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

it. Preset pendulum apparatus comprising an escapement shaft mounted for angular movement about an axis and having an annular circumferential groove with radial projections; pendulum means fixedly attached to said shaft; a biassed rotary balance wheel having teeth and being located in a plane of symmetry passing through said axis; and escapement means in the form of an integral body cast about said control shaft in the region of said groove and thereby fixedly secured to said control shaft, said escapement means including two axially spaced pallets having cam faces located in said plane and engaged by successive teeth so that said escapement means, said control shaft, and said pendulum means are driven in angular strokes about said axis, said escapement means having at least one planar abutment face defining a predetermined angle with said plane of symmetry and adapted to engage a fixed setting surface defining the same predetermined angle with said pendulum means during attachment of said pendulum means to said shaft so that said pendulum means is in the center position of the oscillation thereof when said balance wheel engages said cam faces of said pallets.

2. Pendulum apparatus as claimed in claim 1 wherein said pendulum means includes a pendulum holder and a pendulum mounted in said pendulum holder; and wherein said pendulum holder is cast about said shaft.

3. Pendulum apparatus as claimed in claim 2 wherein said shaft has an other circumferential groove with radial projections in the region of said cast pendulum holder.

4. Pendulum apparatus as claimed in claim 2 wherein said pendulum holder and said escapement means are simultaneously cast injection molded bodies consisting of a synthetic material.

5. Preset pendulum apparatus comprising an escapement shaft mounted for angular movement about an axis; pendulum means fixedly attached to said shaft; a biassed rotary balance wheel having teeth and being located in a vertical plane of symmetry passing through said axis; and escapement means in the form of an integral cast body fixedly secured to said shaft and including two axially spaced pallets located on top of a horizontal plane passing through said axis and at least partly located at opposite sides of said vertical plane of symmetry, said pallets having cam faces located in said plane of symmetry and engaged by successive teeth so that said escapement means, said shaft, and said pendulum means are driven in angular strokes about said axis, said cast body having two planar abutment faces located below said horizontal plane and extending in an axial direction substantially over the whole length of said escapement means at right angles to each other, while including each an angle of 45 with said plane of symmetry, said abutment faces being adapted to respectively engage two fixed setting surfaces each defining an angle of 45 with said pendulum means during attachment of the latter to said shaft so that said pendulum means is in the center position of the oscillation thereof when said balance wheel engages said cam faces of said pallets, said body having further two horizontal marginal faces in said horizontal plane forming axially extending outer edges with said abutment faces,

7 said pallets extending from said horizontal marginal faces, respectively, at opposite axial ends of said body to said vertical plane of symmetry and having said cam faces axially spaced in said vertical plane of symmetry.

6. Pendulum apparatus as claimed in claim wherein said body includes a semicircular projection forming axially extending inner edges with said marginal faces and projecting above said horizontal plane; and wherein said pallets are curved and project radially from said semi-circular projection at the axial ends of the latter, said curved pallets and semicircular projections having centers located in said axis of said control shaft and being integral parts of said body; and wherein said pallets have curved outer surfaces forming horithe radial height to said curved outer surfaces. 

1. Preset pendulum apparatus comprising an escapement shaft mounted for angular movement about an axis and having an annular circumferential groove with radial projections; pendulum means fixedly attached to said shaft; a biassed rotary balance wheel having teeth and being located in a plane of symmetry passing through said axis; and escapement means in the form of an integral body cast about said control shaft in the region of said groove and thereby fixedly secured to said control shaft, said escapement means including two axially spaced pallets having cam faces located in said plane and engaged by successive teeth so that said escapement means, said control shaft, and said pendulum means are driven in angular strokes about said axis, said escapement means having at least one planar abutment face defining a predetermined angle with said plane of symmetry and adapted to engage a fixed setting surface defining the same predetermined angle with said pendulum means during attachment of said pendulum means to said shaft so that said pendulum means is in the center position of the oscillation thereof when said balance wheel engages said cam faces of said pallets.
 2. Pendulum apparatus as claimed in claim 1 wherein said pendulum means includes a pendulum holder and a pendulum mounted in said pendulum holder; and wherein said pendulum holder is cast about said shaft.
 3. Pendulum apparatus as claimed in claim 2 wherein said shaft has an other circumferential groove with radial projections in the region of said cast pendulum holder.
 4. Pendulum apparatus as claimed in claim 2 wherein said pendulum holder and said escapement means are simultaneously cast injection molded bodies consisting of a synthetic material.
 5. Preset pendulum apparatus comprising an escapement shaft mounted for angular movement about an axis; pendulum means fixedly attached to said shaft; a biassed rotary balance wheel having teeth and being located in a vertical plane of symmetry passing through said axis; and escapement means in the form of an integral cast body fixedly secured to said shaft and including two axially spaced pallets located on top of a horizontal plane passing through said axis and at least partly located at opposite sides of said vertical plane of symmetry, said pallets havIng cam faces located in said plane of symmetry and engaged by successive teeth so that said escapement means, said shaft, and said pendulum means are driven in angular strokes about said axis, said cast body having two planar abutment faces located below said horizontal plane and extending in an axial direction substantially over the whole length of said escapement means at right angles to each other, while including each an angle of 45* with said plane of symmetry, said abutment faces being adapted to respectively engage two fixed setting surfaces each defining an angle of 45* with said pendulum means during attachment of the latter to said shaft so that said pendulum means is in the center position of the oscillation thereof when said balance wheel engages said cam faces of said pallets, said body having further two horizontal marginal faces in said horizontal plane forming axially extending outer edges with said abutment faces, said pallets extending from said horizontal marginal faces, respectively, at opposite axial ends of said body to said vertical plane of symmetry and having said cam faces axially spaced in said vertical plane of symmetry.
 6. Pendulum apparatus as claimed in claim 5 wherein said body includes a semicircular projection forming axially extending inner edges with said marginal faces and projecting above said horizontal plane; and wherein said pallets are curved and project radially from said semi-circular projection at the axial ends of the latter, said curved pallets and semicircular projections having centers located in said axis of said control shaft and being integral parts of said body; and wherein said pallets have curved outer surfaces forming horizontal axially extending edges with said abutment faces, respectively, and being continuations of said outer edges of said marginal horizontal faces.
 7. Pendulum apparatus as claimed in claim 6 wherein said curved pallets have upper ends having on one side said cam faces engaged by said teeth, and having on the other side other cam faces tapering forward and upward.
 8. Pendulum apparatus as claimed in claim 7 wherein said other tapered cam faces extend from about half the radial height to said curved outer surfaces. 